1. Field of the Invention
The present invention relates to a belt cleaning apparatus and an image forming apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus is employed a method in which a toner image is obtained by developing an electrostatic latent image on an electrostatic latent image bearing member with a toner and the toner image is transferred to a recording medium to form the toner image on the recording medium. As a transfer method in an image forming apparatus is used a method in which a toner image formed on an electrostatic latent image bearing member is transferred to an intermediate transfer belt which bears and conveys a toner image transferred thereto, the toner image transferred to the intermediate transfer belt is electrostatically moved to a recording medium by a transfer section which faces the intermediate transfer belt with the recording medium interposed therebetween. A belt cleaning apparatus is arranged to remove a residual toner remaining on an outer peripheral surface of an intermediate transfer belt after transferring a toner image to a recording medium.
A blade type belt cleaning apparatus is widely used as a belt cleaning apparatus. The blade type belt cleaning apparatus scrapes off a residual toner remaining on an outer peripheral surface of the intermediate transfer belt by abutting a plate-like cleaning blade on a surface of an intermediate transfer belt which bears a toner image transferred thereon.
In such a blade type belt cleaning apparatus, removal efficiency of the residual toner remaining on the outer peripheral surface of the intermediate transfer belt can be improved by increasing pressing pressure of the cleaning blade against the intermediate transfer belt. However, when the pressing pressure of the cleaning blade against the intermediate transfer belt is increased, an abutting portion of the cleaning blade bites too much from the outer peripheral surface of the intermediate transfer belt into the inside thereof in the thickness direction, and reversal phenomenon that the cleaning blade rides up due to rotation of the intermediate transfer belt occurs. Those problems decrease removal efficiency of the residual toner. The reversal phenomenon that the cleaning blade rides up markedly occurs at a portion corresponding to an end of a width direction of the intermediate transfer belt among the abutting portions of the cleaning blade to the intermediate transfer belt.
To solve such a problem, Japanese Unexamined Patent Publication JP-A 8-171286 (1996) discloses a belt cleaning apparatus that has a cleaning blade with a slit formed in a boundary portion of first cleaning edge parts corresponding to ends of an intermediate transfer belt within a snaking range of the intermediate transfer belt, and second cleaning edge parts corresponding to an effective image range of the intermediate transfer belt except the first cleaning edge part.
In recent years, an intermediate transfer belt comprising a base material made of polyimide, and an elastic layer formed on a surface of the base material is being used in an electrophotographic image forming apparatus in order to improve a toner image bearing ability of an intermediate transfer belt and transferability of a toner image to a recording medium.
When applying the belt cleaning apparatus disclosed in JP-A 8-171286 as an apparatus for removing a residual toner remaining on an outer peripheral surface of an intermediate transfer belt having an elastic layer, the cleaning blade with the slit formed abuts on the elastic layer on the outer peripheral surface of the intermediate transfer belt.
In the belt cleaning apparatus disclosed in JP-A 8-171286, the slit in the cleaning blade is impossible to remove the residual toner, and thus it is hard to say that the removal efficiency of the residual toner is sufficient.
Furthermore, since the elastic layer on the outer peripheral surface of the intermediate transfer belt is a layer which easily undergoes elastic deformation, not only that uniform cleaning performance for the outer peripheral surface of the intermediate transfer belt is not obtainable as the abutting portion of the cleaning blade, especially the end of the slit bites too much from the outer peripheral surface of the intermediate transfer belt into the inside thereof in the thickness direction, but also that the reversal phenomenon that the cleaning blade rides up due to rotation of the intermediate transfer belt occurs, and thereby the removal efficiency of the residual toner decreases.